 window.onload = function() {
        getRem(750, 100)
      };
      window.onresize = function() {
        getRem(750, 100)
      };

      function getRem(pwidth, prem) {
        var html = document.getElementsByTagName("html")[0];
        var oWidth = document.body.clientWidth || document.documentElement.clientWidth;
        html.style.fontSize = oWidth / pwidth * prem + "px";
      }